Patent GB-573745-A (GB)
Title: Improvements in or relating to photographic light-sensitive elements
Filed: 1944-02-03
Abstract: A process for improving the quality of an image developed in a silver halide emulsion layer in a photographic element comprises adding to the emulsion a substantially water-insoluble, colourless, and non-colour-forming metal derivative of a compound which is a 5-mercaptotetrazole, a 5-mercapto-1 : 3 : 4-triazole, a heterocyclic compound with two ring N atoms and 1, 2, or 3 S atoms attached to C atoms which next to the N atoms, or a mono- or di-mercaptomonazole, the metal derivative being soluble or decomposable during treatment of the element with processing baths subsequent to the development of the element.  The metal derivative may be a silver, nickel, copper, iron (ferric), cobalt, uranium, aluminium, chromium, thallium, lead, cadmium, zinc, antimony, bismuth, iron (ferrous), or gold derivative of a 5-mercaptotetrazole (e.g. 1-phenyl - 5 - mercaptotetrazole, 1 - d - naphthyl-5 - mercaptotetrazole, 1 - B - naphthyl - 5 - mercaptotetrazole, 1 - p - diethylaminophenyl-5 - mercaptotetrazole, 1 - o - methoxyphenyl-5 - mercaptotetrazole, 1 - p - chlorophenyl - 5 - mercaptotetrazole, 1 - benzyl - 5 - mercaptotetrazole, 1 - cyclohexyl - 5 - mercaptotetrazole, 1 - methyl - 5 - mercaptotetrazole, or 1 - ethyl - 5-mercaptotetrazole), of a 5-mercapto-1 : 3 : 4-triazole (e.g. 1 : 2-dimethyl-5-mercapto-1 : 3 : 4-triazole, 1 - ethyl - 2 - methyl - 5 - mercapto-1 : 3 : 4-triazole, 1-phenyl-2-methyl-5-mercapto-1 : 3 : 4-triazole, 1-phenyl-5-mercapto-1 : 3 : 4-triazole, 1-benzyl-5-mercapto-1 : 3 : 4-triazole, 1 - methyl - 2 - ethyl - 5 - mercapto - 1 : 3 : 4 - triazole, 1 - methyl - 2 - n - hexyl - 5 - mercapto-1 : 3 : 4-triazole, 1 - p - hydroxyphenyl - 2 - methyl-5-mercapto-1 : 3 : 4-triazole, 1-p-aminophenyl - 2 - methyl - 5 - mercapto - 1 : 3 : 4-triazole, 1 - d - naphthyl - 2 - phenyl - 5 - mercapto-1 : 3 : 4-triazole, 2-d-naphthyl-5-mercapto-1 : 3 : 4-triazole, or 1-2-diphenyl-5-mercapto-1 : 3 : 4-triazole), of the sulphur-substituted heterocyclic nitrogen compound containing 2 nitrogen atoms in the ring (e.g. 2 : 5-dimercapto-1 : 3 : 4-thiodiazole, 2-mercapto-5-amino-1 : 3 : 4-thiodiazole, 1-mercapto-4-hydroxyphthalazine, 1 : 4-dimercaptophthalazine, 2-thio-5-mercapto-3-methyl-1 : 3 : 4-thiodiazoline, 2-hydroxy-4-mercaptopyrimidine, 2 : 4 - dimercaptopyrimidine, 2 : 4 - dimercaptoquinazoline, or trithiobarbituric acid, and 2-mercapto - 4 - phenyl - 5 - keto - 1 : 3 : 4 - thiodiazoline), of a dimercaptomonazole (e.g. 2 : 4-dimercaptoquinoline), or of a monomercaptomonoazole (e.g. 2-mercaptobenzthiazole, 2-mercaptobenzoxazole, 2-mercaptoquinoline, 2-mercapto-6 : 7-benzbenzthiazole, or 4-mercaptoquinoline).  The emulsion may be a silver chloride, chlorobromide, bromide, or iodobromide emulsion.  In example 1, a solution of 1-phenyl-2-methyl-5-mercapto-1 : 2 : 4-triazole in aqueous sodium carbonate solution is used. Specifications 561,875 and 573,105 are referred to. 1-chloro-4-hydroxyphthalazine and 1 : 4-dichlorophthalazine are prepared by heating phthalylhydrazide with excess POCl3. 1-Mercapto-4-hydroxyphthalazine is prepared by heating 1-chloro-4-hydroxyphthalazine with excess alcoholic potassium hydrosulphide in a sealed tube.  1 : 4-Dimercaptophthalazine is prepared by refluxing together 1 : 4-dichlorophthalazine and excess alcoholic potassium hydrosulphide.  2 : 4-Dimercaptoquinoline is prepared by heating 2 : 4-dichloroquinoline with thiourea in alcoholic solution.